The Verge has a learned a few interesting things about Google deprecating EAS and how this will affect Windows Phone users. As it turns out, Google informed Microsoft it was planning to remove EAS in the summer of last year, but without giving a firm date. Microsoft has been trying to get a six-month extension from Google, but so far with no luck. In the meantime, Microsoft is also working on adding CardDAV and CalDAV support to Windows Phone - so yay open standards.

You said that EAS was both open and documented. I simply pointed you that it may be documented, but it is not open. Microsoft has not claimed it is open, specially when contrasted with the official definition that Microsoft employs for the term "open." I honestly fail to see what else is there to discuss regarding this matter.